A hydraulic drive control device which is capable of translating the
effect of oil pressure loss reduction into the effect of fuel consumption
reduction that is very real to the user. The hydraulic drive control
device has (i) a driving hydraulic circuit for driving a hydraulic
actuator by supplying pressure oil to or draining it from the hydraulic
actuator through control valves, the pressure oil being discharged from a
hydraulic pump driven by an engine and (ii) a quick return circuit for
directly flowing part of hydraulic oil discharged from the hydraulic
actuator back to a tank, while the hydraulic actuator being driven. The
hydraulic drive control device also includes an engine controller for
controlling the output of the engine such that the output of the engine
is restricted when the quick return circuit is opened.